22.5.3: The down sheep

Question 1

Differentials for a down sheep

Answer 1

• Pregnancy toxaemia
• Hypocalcaemia
• Trauma
• Scrapie
• Lameness
• Respiratory disease
• Listeria
• Hypomagnesaemia
• Clostridial disease - more likely to present as sudden death

Question 2

Which ewes are more prone to hypocalcaemia?

Answer 2

Hypocalcaemia occurs in late pregnancy
* Older and thinner ewes more prone
* Carrying multiple foetuses increases risk
* Any stressor can trigger the condition

Question 3

Treatment of hypocalcaemia in the ewe and what response you would expect with time limits

Answer 3

• 25-40ml 40% calcium borogluconate over 30-60 seconds IV
• Typically see eructation after 1-2 mins, stand after 5 mins, then urination/defecation and rejoining the flock

Question 4

What are normal serum levels of the following elements for ewes:
Ca
P
Mg

Answer 4

• Ca - 2.6mmol/L
• P - 1mmol/L
• Mg - 1.3mmol/L

Question 5

What are the risk factors for pregnancy toxaemia?

Answer 5

• Occurs in late pregnancy
• Older or thinner ewes are more prone
• Carrying multiple foetuses increases the risk
• Any stressor can trigger the condition

Question 6

Why not just feed the sheep loads to prevent pregnancy toxaemia?

Answer 6

• Perversely, overfeeding increases the pregnancy toxaemia risk as it deregulates the insulin response
• Feeding more increases the milk fever risk as there is deregulation of the parathyroid hormone response
• Overfeeding makes vaginal prolapses more likely and dystocia more likely (fat in pelvic canal with oversized foetus)
• Feed is expensive

Question 7

Management of pregnancy toxaemia (sheep)

Answer 7

• IV glucose (will bring the ewe out of comatose state)
• Oral propylene glycol (oral glucose would just get used up by rumen flora so not effective)
• Consider inducing parturition with steroids/PGF2a
• Encourage eating: consider minerals in molasses to make the minerals more palatable (be mindful of levels and avoid overdose), give yeast with propylene glycol drench to promote good ruminal health, give Vitamin B12

Question 8

Clinical signs of hypocalcaemia (sheep)

Answer 8

• Stiff gait, ataxia
• Muscle tremors
• Weakness
• Lying on brisket, sometimes with a frog-legged position where hindlimbs are extended

Question 9

How might you differentiate pregnancy toxaemia from hypocalcaemia in the ewe?

Answer 9

In pregnancy toxaemia
* Ewe is separated from the mob
* Ewe is drowsy/comatose
* Ewe is not eating
* Ewe shows nervous system signs such as tremors and blindness
* Pregnancy toxaemia has a long duration (ewe lying down for 3-4 days) whereas hypocalcaemia kills the ewe comparatively quickly

Question 10

What is normal blood glucose for a ewe?

Answer 10

50-80mg/dL

Question 11

What are some other differentials for a down sheep presenting with altered mentation and nervous system signs, aside from pregnancy toxaemia?

Answer 11

• Rabies
• Acidotic due to grain overload
• Brain abscesses
  Gather a thorough history and check for variety of neuro signs and dietary indiscretion.

Question 12

True/false: when a sheep presents with staggers, you should start with black top Mg IV, then follow up with red top Ca and Mg SC.

Answer 12

False
Do not give black top bottle IV - this will kill the animal!
Give red top (40% Ca + 5-10% Mg) IV
Then follow with black top SC (this provides more Mg)

Question 13

What is a common finding from the history of animals that present with hypomagnesaemia (staggers)?

Answer 13

Recent release to fast-growing, lush spring pasture / sometimes pasture with high potassium fertiliser recently put onto it (this inhibits Mg uptake)

Question 14

Describe the prevention of staggers in sheep

Answer 14

• Increase gut transit times by feeding higher fibre diet -> this helps increase the absorption of available Mg
• Routine soil analysis to assess Mg levels of soil, and use of Mg limestone to maintain
• Modify bagged fertiliser applications so K applications are carried out later in the season
• A regular supply of Mg in the diet (=offer free access to minerals)